The given function is,
f( x )=2 x 2 −1
At x=3, the function becomes,
f( 3 )=2 ( 3 ) 2 −1 =17
The left hand limit of the function at x=3 is,
LHL= lim x→ 3 − f( x ) = lim x→ 3 − ( 2 x 2 −1 ) =17
The right hand limit of the function at x=3 is,
RHL= lim x→ 3 + f( x ) = lim x→ 3 + ( 2 x 2 −1 ) =17
It can be observed that, at x=3, LHL=RHL=f( 3 )=17.
Therefore, the function is continuous at x=3.